ABSTRACT
If one shakes pure water, no bubbles are observed at the surface. On the other hand, if one shakes a soap solution, bubbles appear at the surface after shaking. Bubbles are also observed on the shores of lakes. This shows that some kind of surface thin liquid †lm is present in the soap solution. The formation and structure of thin liquid €lms (TLF; such as in foams or bubbles) is the most fascinating phenomena that mankind has studied over many decades. Gas bubbles have been investigated by scientists in a large number of applications in everyday life. It may be accepted that this structure is the closest one comes to observing molecules by the naked eye. TLF is thus the thinnest object one can see without the aid of any kind of microscope. One of the most commonly known thin liquid †lm structures is the soap bubble or bubbles formed in detergent solutions (such as in dishwashing solutions). Everyone has enjoyed the formation of soap bubbles and the view of the rainbow colors. It may look as if the bubble formation and stability does not have such a great consequence, but in everyday life, bubbles play an important role (for example, from lung function to beer and champagne). In this chapter, the formation and stability of bubbles will be described. Further, even though one cannot see or observe the surface layer of a liquid directly, thin liquid †lms allow one to make some observations that provide much useful information (Adamson and Gast, 1997; Birdi, 2002, 2009, 2010a, 2010b).
